Hydrocolloid adhesive compositions, as well as wound dressings and ostomy products formed from these adhesive compositions, have been known for many years. Typically, these compositions comprise a blend of a polymer matrix, such as a rubbery elastomer like polyisobutylene, in combination with one or more water-soluble or water-swellable hydrocolloids, such as a dry powdered mixture of pectin, gelatin and carboxymethylcellulose. When included in a wound dressing or ostomy seal, the adhesive composition is usually coated on at least one surface of a water-insoluble film. See e.g., U.S. Pat. Nos. 3,980,084, 3,877,431, 3,532,679, and 3,339,546, and European patent application No. 0343807. A commercially available example of a composition of this type is STOMADHESIVE.TM. (E. R. Squibb & Sons Inc., Princeton, N.J.), which is used as a skin barrier around stomas to prevent skin breakdown by the corrosive fluids discharged by the stoma.
A major problem with many conventional hydrocolloid adhesive compositions is their susceptibility to breakdown upon exposure to wound exudate and body fluids (i.e. their lack of structural integrity after being hydrated). When the compositions are used as skin barriers, e.g., around stomas, some absorption of fluid is desirable, but excessive swelling causes the composition to lose its moisture seal with the skin. Leakage occurs and the barrier must be replaced more often than is desirable.
Furthermore, when the adhesive compositions are used as wound dressings, the compositions tend to dissolve upon exposure to wound exudate and form a gel on the surface of the wound. When the dressing is removed, a residue remains on the wound requiring removal, typically by irrigation. When this breakdown occurs the dressings may also lift off the wound and allow leakage of wound exudate onto clothing and bedding.
Accordingly, a number of attempts have been made to improve the integrity of hydrocolloid adhesive compositions, and the resulting wound dressings and ostomy products.
U.S. Pat. No. 4,496,357 describes the incorporation of fumed silica into hydrocolloid compositions to control swelling.
U.S. Pat. No. 4,551,490 describes a hydrocolloid adhesive composition of a homogenous blend of mineral oil, one or more polyisobutylenes alone or in combination with an elastomer such as butyl rubber, styrene radial or block copolymers, water-soluble hydrocolloid gums, water-swellable cohesive strengthening agents, and a tackifier. Both the elastomer and water-swellable agents are said to add cohesive strength to the composition, while the styrene radial or block copolymers are said to provide extensibility and recovery from modular strains associated with hydration. See also, U.S. Pat. Nos. 4,204,540, 4,192,785, and 4,166,051.
U.S. Pat. No. 4,952,618 discloses a hydrocolloid adhesive composition formed from a rubbery elastomeric base having hydrocolloid particles, at least some of which are polycationic, dispersed therein. The composition is said to exhibit improved integrity attributable to the polycationic particles contained in the compositions, particularly when combined with anionic hydrocolloid particles, either alone, or further mixed with neutral hydrocolloid particles.
In a different approach, U.S. Pat. Nos. 4,538,603 and 4,728,442 disclose a granular wound packing that is covered with a separate occlusive dressing. In general, the occlusive dressing component can include a variety of hydrocolloid materials in combination with one or more pressure sensitive adhesive elastomers, such as polyisobutylene, and one or more thermoplastic elastomers, such as butyl rubber and styrene copolymers.
Another manner of addressing lack of structural integrity is to provide hydrocolloid adhesive compositions where one or more of the polymeric components are chemically or physically cross-linked. For example, U.S. Pat. No. 4,768,503 provides a adhesive composition of one or more chemically cross-linked hydrophilic polymers in combination with a support matrix of a high molecular weight hydrophobic polymer.
U.S. Pat. Nos. 4,477,325 and 4,738,257 describe incorporating into a hydrocolloid composition a mixture of a copolymer resin of ethylene and vinyl acetate (EVA). After mixing and molding, the composition is subjected to ionizing radiation to form cross-linked polymer networks of the EVA or EVA with another cross-linkable resin. The cross-linked matrix is said to provide controlled swelling.
In a similar vein, U.S. Pat. No. 4,231,369 and European Patent Publication No. 0272149 disclose various hydrocolloid materials dispersed within a physically cross-linked gel-like phase. In general, the gel-like phase is comprised of elastomeric materials, such as A-B-A block copolymers, as well as certain ethylene/propylene copolymers, that are said to be physically cross-linked due to phase separation and reformation of the materials after melt processing.
In general, the efforts to date at providing a high integrity hydrocolloid adhesive compositions, and associated wound dressings and ostomy barriers, have not proven to be very effective. Furthermore, even when such materials demonstrate improved integrity, such an improvement has typically been at the expense of a number of other desirable properties, such as absorption, good edge adhesion, shear holding power, cohesive strength, lack of adhesive residue, reduced adhesive cold-flow, increased conformability and elasticity, and decreased skin sensitivity.